_content/blog: fix link in loopvar-preview post

A link to the Go release policy was broken. Fix it.

Change-Id: Idd158e32063a07d2924c1cdf50a0293e0a891a70
Reviewed-on: https://go-review.googlesource.com/c/website/+/529257
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Tim King <taking@google.com>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Auto-Submit: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Reviewed-by: Damien Neil <dneil@google.com>

_content/blog/loopvar-preview.md

@@ -148,7 +148,7 @@ We included a special case with the same effect in
 the point releases Go 1.20.8 and Go 1.19.13,
 so when Go 1.22 is released,
 code written depending on the new semantics will never be compiled with
-the old semantics, unless people are using very old, unsupported Go versions](/doc/devel/release#policy).
+the old semantics, unless people are using very old, [unsupported Go versions](/doc/devel/release#policy).
 
 
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